The present invention relates generally to miniature, electrically powered vehicles which are traditionally used as toys in association with a continuous track which has at least one pair of electric rails associated with it. The vehicle has electrical contacts which engage the pair of rails, thereby delivering electric power to the motor of the vehicle. Such cars are depicted in prior patents including, for example, U.S. Pat. Nos. 3,086,319 to M. G. Frisbie et al and 2,690,626 to G. R. Gay et al.
In many vehicles of this type, the four wheels are mounted to a rigid frame and a guide pin or other protrusion is provided at the forward end of the car, extending down below the level of the front wheels of the car. The guide pin is engaged within a guide slot in the track, and electrical pick-ups are fixed on either side of the guide pin in the car in order to make sliding electrical contact with the rails as the car moves around the track. The track may have several such slots so that several cars can be operated at the same time.
In some instances, such cars operate without a guide pin and the tracks they operate on are provided with multiple pairs of electrical rails such that the electrical pick-ups are substantially continuously engaged with one or another pair of rails along the width of the track. Such products are shown, for example, in U.S. Pat. No. 3,486,271 to R. Feikemer.
Although products of this general type have been successfully manufactured and marketed, there have been a number of problems which have long existed but which have not heretofore been fully solved. Among the most significant of these problems is the insufficient traction force which has allowed the wheels of such electrically powered vehicles to needlessly spin on attempted acceleration and to thereby lose a great deal of their speed. Another serious problem is that of spinning out on curves as a result of the necessarily low weight of the toy cars. These problems have been reduced by the use of larger rear tires of soft material such as foam, plastic or rubber, as opposed to the harder rubber-like tires which had been used. Although the soft and wide tires have produced some improvement in operation of the cars, the low traction and spin problems have continued.
It has been clear to those skilled in this art that increasing the weight of the vehicle would increase the normal force of a vehicle against the track, thereby increasing the frictional forces of traction forces between the vehicle wheels and the track surface. However, the simple expedient of adding weight to the toy vehicle is an unsuccessful alternative because for each increment of additional weight added to the vehicle, one must add additional motive power, i.e., it is required to provide a bigger and/or stronger motor. Not only does this requirement increase the cost of the end product, it is often impossible to obtain any substantial increase in the power of the motor because of the extremely small size of the vehicles, which, in their preferred embodiments are approximately HO gauge.
It has also been known that one could increase the normal force exerted by a car riding upon an iron or steel surface by mounting permanent magnets on the car at a location close enough to the surface such that magnetic attraction would increase the effective normal force on the car. This expedient, however, has never proved successful because the weight of magnets which are effective when displaced from the track pose the same need for increased power as was required for normal weight increases, and the cost of additional magnetic material exceeds the benefit derived in the toy vehicle designs of the prior art. In general, a design providing improved steering performance has been elusive.